Some settings in properties > world are missing?
This is because you are using Cycles as your render engine.

Here is the correct wiki page.

Those settings you saw are only there when Blender Render (also known as Blender Internal or BI) is selected as the active render engine in the Info panel > Header:



Note you can do everything that you could do using those settings in BI in Cycles, however the process for setting some of the things up is different in Cycles.




The number of samples is controlled in Properties > Render settings > Sampling:



Note that samples behave differently in cycles and BI, see this question. 
AO in cycles is always added, if you want to multiply you must enable the AO pass in Render Layers > Passes:



And then multiply it with your render in the compositor:


The world background color can be set either from the world settings or the world nodes:



Both settings are the same, setting one sets the other. If you want sky textures or gradients, use Texture and Mapping nodes.